The present invention relates to a sewing machine for sewing edge hems of an upper fabric and a lower fabric together that are fed to a needle drop point in an overlapped manner, and particularly to a sewing machine equipped with an uncurling device for straightening curls formed in the edge hems.
In performing sewing by using an overlock sewing machine for overedge-chain stitching edge hems of an upper fabric and a lower fabric that are fed to a needle drop point in an overlapped manner, particularly when the upper fabric and lower fabric are, i.e., knitted fabrics that tend to exhibit a tendency to curling, it would often be the case that both fabrics were fed to the needle drop point with their edge hems being curled to outside or inside and sewn together with these edge hems being in flapped conditions.
Such sewing causing degradations in qualities of obtained sewn articles, operators would manually straighten curls in the edge hems prior to feeding them into the needle drop point when performing sewing with the overlock sewing machine, which resulted in a great deal of work for this straightening. Further, in case the upper fabric and lower fabric are knitted materials or the like that are of rich elasticity, a drawback was presented in that high skill was required for straightening the curls without being accompanied by expansion of these fabrics.
An uncurling device that has been devised with the aim of solving these problems is disposed in Utility Model Examined Publication No. 7-44310(1995) co-owned by the applicant of the present invention, wherein the device is employed by being attached to a front portion of a needle drop point of a sewing machine for performing uncurling as once it had been manually performed by an operator.
Manual uncurling is performed through the following steps: a finger is inserted between the upper fabric and the lower fabric; other fingers are respectively placed on an upper surface of the upper fabric and a lower surface of the lower fabric for pinching the upper fabric and the lower fabric at proximities to their edge hems; and these pinched fabrics are fed to the needle drop point while the both edge hems are stretched by the fingers, thereby the curled portions are straightened (uncurled). The above uncurling device is arranged in that a plurality of straightening pieces that respectively simulate those fingers as used in the above manual operations is provided, in that the upper fabric and the lower fabric are pinched between these pieces, therefore uncurling is performed as feeding of both of the fabrics while the edge hems are stretched by the simulated fingers.
However, the uncurling device as disclosed in the above Utility Model Examined Publication 7-44310 is of complicated arrangement comprising the above plurality of straightening pieces (simulated fingers) and further comprising a mechanism for moving each of the straightening pieces up and down separately to pinch the upper fabric and lower fabric appropriately. Thus, the whole mechanism requires a bulky space in a front portion of the sewing machine.
Curls at the edge hems of fabrics that need to be straightened include outside curls with curls being formed at the edge hems of upper fabric or lower fabric in directions facing away from each other as well as inside curls with curls being formed in directions approaching towards each other. A drawback was consequently presented in that in the above uncurling device, forms for pinch-holding between the straightening pieces needed to be varied in accordance with combinations of curling shapes of the upper fabric and lower fabric and in that a great deal of work was required for setting upper fabric and lower fabric before sewing.